Highly active antiretroviral therapy (HAART) involves the use of a combination of three different classes of antiviral compounds for the treatment of HIV infection. These compounds include the nucleoside reverse transcriptase inhibitors, non-nucleoside reverse transcriptase inhibitors and protease inhibitors.
HAART has improved the outcomes in HIV-1 infected patients, however, its use is complicated by metabolic adverse events that are collectively termed HAART-associated lipodystrophy Carr, A., Aids, 17 Suppl 1: p. S141-8 (2003). These metabolic changes include fat atrophy/hypertrophy, dyslipidemia and insulin resistance. Although the mechanistic basis underlying lipodystrophy associated with HAART is poorly understood, the associated metabolic abnormalities are well established cardiovascular risk factors (Grinspoon, S. et al., N Engl J Med, 352(1):48-62 (2005)).
Genetic association studies performed by the inventors revealed that a single nucleotide polymorphism in the resistin gene provided evidence of an association with a risk of developing lipodystrophy in patients enrolled on HAART. Resistin was originally cloned as an adipocytokine that provides a mechanistic link between obesity and insulin resistance (Steppan, C. M., et al., Nature, 409(6818):307-12 (2001)). In mice, hyperresistinemia results in insulin resistance (Rajala, M. W., et al., J Clin Invest, 111(2):225-30 (2003)) and knockout studies have shown that resistin deficient mice are protected from insulin resistance (Banerjee, R. R., et al., Science, 303(5661):1195-8 (2004)). In humans, resistin has been shown to be associated with components of lipodystrophy syndrome in some (Conneely, K. N., et al., Diabetologia, 47(10): 1782-8 (2004), Mattevi, V. S., et al., Hum Genet, 115(3):208-12 (2004)), but not all studies (Ochi, M., et al., Diabetes Res Clin Pract, 61(3): p. 191-8 (2003)).
Aspartyl proteases comprise a group of proteolytic enzymes that share the same catalytic mechanism (Dash, C., et al., Crit. Rev Biochem Mol Biol, 38(2):89-119 (2003)). Members of this family include HIV-1 protease and at least five human enzymes. In pre-clinical development, the human aspartyl proteases are used to counter-screen HIV-1 protease inhibitors for selectivity toward HIV-1 protease. However, selectivity toward HIV-1 protease can vary widely across HIV-1 protease inhibitors (Ohtaka, H., et al., Int J Biochem Cell Biol, 36(9):1787-99 (2004)).
The present invention provides, for the first time, an in vitro assay for identifying protease inhibitors that either lack or have a lower propensity for causing metabolic abnormalities in patients.
The present invention also provides genetic polymorphisms in the resistin gene which may cause alterations in the function and/or expression of resistin. Such polymorphisms may genetically predispose certain individuals to an increased risk of developing metabolic abnormalities, particularly in response to HIV protease-inhibitor therapy. Genotypes of such polymorphisms may predict each individual's susceptibility to metabolic abnormalities, and thus will be useful in identifying a group of patients that may be subject to modified HAART treatment regimens. Alternatively, the identification of such a group may preclude one or more individuals within said group from being administered HAART therapy.